The present invention relates generally to methods for the synthesis of various solids such as diamonds, diamond films, boron nitride and other similar materials. This invention specifically relates to utilizing novel sources of reaction species (e.g., in the case of diamond formation, novel sources of carbon and/or hydrogen and/or seeds) for the manufacture of various materials and the use of such materials for various commercial purposes.
There are various known methods for producing synthetic diamond. In a first method, diamond grit may be synthesized by precipitating diamond from carbon contained within a metal solution at high temperatures (e.g., 1400xc2x0 C.,) and high pressures (e.g., 60 Kbar). The resulting diamond which is produced at these high temperatures and high pressures may be free of second phase inclusions, but generally contains significant concentrations of dissolved nitrogen and metal (e.g., nickel, iron, cobalt, etc.).
In a second technique, diamond powder may be produced by shock wave synthesis, wherein an explosive charge is utilized to shock a mixture of carbon and a metal solvent/catalyst. An example of the shock wave synthesis technique can be found in U.S. Pat. No. 3,401,019, which issued on Sep. 10, 1968, in the names of Cowan et al. Drawbacks of the shock wave synthesis procedure are that the diamond which is produced is routinely contaminated with dissolved nitrogen metal (e.g., iron). In addition, the recovery of diamond particles produced requires elaborate chemical processing to separate the diamond particles from the surrounding materials within the reaction chamber (e.g., graphite and metal). Moreover, this method typically produces only submicron diamond powders.
In a third technique, diamond powder can be made by precipitation of diamond within certain amorphous metals which are saturated with carbon. For example, U.S. Pat. No. 4,485,080 to Shingu et al., which issued on Nov. 27, 1984, describes a multi-step process for the rapid solidification of carbon-containing alloys followed by the precipitation of diamond particles within the amorphous metal at temperatures above 100xc2x0 C. The diamond is thereafter recovered from the metal by acid digestion.
In a more recent development, thin diamond films are synthesized from the vapor phase by an activated chemical vapor deposition (CVD) process. Typically, during such CVD processes, diamond particles nucleate on the surface of an appropriate substrate heterogeneously and thereafter grow in size. The particles thus produced may be widely separated or may be close enough to coalesce into a continuous diamond film. Exemplary techniques showing various aspects of the CVD process can be found in the following patents: U.S. Pat. No. 4,882,138, which issued on Nov. 21, 1989, in the name of John Pinneo, which discloses the use of the combination of diamond particles, atomic hydrogen and a gaseous carbon source, which, when processed, results in diamond being epitaxially deposited on the diamond particles; U.S. Pat. No. 4,958,590, which issued on Sep. 25, 1990, in the name of Robert Goforth, which discloses a specific microwave assisted CVD process and apparatus; U.S. Pat. No. 4,985,227, which issued on Jan. 15, 1991, in the names of Ito et al., which discloses contacting a substrate material with a gaseous source of excited carbon monoxide and excited hydrogen and causing diamond to be deposited onto the substrate; and U.S. Pat. No. 5,112,643, which issued on May 12, 1992, in the names of Ikegaya et al., which discloses the use of a raw material gas which includes a carbon source and hydrogen and activating the raw material gas by a thermoelectron-radiating device and by formation of a DC plasma which results in the deposition of a diamond film on the surface of the substrate. In addition, the CVD process for the formation of diamonds has been reviewed by R. C. DeVries, Annual Review of Materials Sciences 17:161 (1987); A. R. Badzian and R. C. DeVries, Mat. Res. Bull. 23:385 (1988); and J. C. Angus and C. C. Hayman, Science 241:915 (1988). The art further shows that graphite can be a source material for the formation of various gaseous carbon-based species which are capable of depositing on a large, single crystal of diamond, B. V. Spitsyn, L. L. Bouilov and B. V. Derjaguin, Prog. Crystal Growth and Charact. 17:79 (1988). However, no one has to date used the principle of CVD processing to form any object other than a polycrystalline diamond film.
Another technique for the formation of diamond is disclosed in U.S. Pat. No. 4,997,636, which issued on Mar. 5, 1991, in the name of Johan Prins. This patent discloses the use of a non-diamond substrate material having a face-centered cubic crystal structure. The substrate is ion implanted with carbon atoms which are later induced to diffuse out of the substrate and grow epitaxially on a surface of the substrate.
A still further technique for the formation of diamond utilizes a combustion flame. Specifically, U.S. Pat. No. 5,075,096, which issued on Dec. 24, 1991, in the names of Tanabe et al. discloses burning a combustible gas containing carbon in a combustion-supporting gas which contains oxygen to create a reduction atmosphere, and precisely controlling the humidity of the reduction atmosphere, and inserting a substrate into the combustible gas flame to form diamond on a surface of the substrate; and U.S. Pat. No. 5,135,730, which issued on Aug. 4, 1992, in the names of Suzuki et al, discloses forming and burning a mixed gas of a hydrocarbon fuel gas and oxygen to form a flame and contacting the flame with the surface of a substrate to form diamond on said substrate.
All of the above-discussed techniques for the production of diamond suffer from one or more of the following drawbacks: high cost of manufacture, complex production equipment, limited sizes and shapes for diamond production, etc. The present invention overcomes the above described disadvantages inherent in various methods known in the art for the synthesis of diamond and other materials. The invention presents a novel method for the manufacture of various materials including, but not limited to, diamond films, shaped diamond products, boron nitride films, shaped boron nitride products, etc.
The present invention relates to a novel process for the manufacture of various solids including diamond films, shaped diamond products, boron nitride films, shaped boron nitride products, silicon films, shaped silicon carbide products, etc. With regard to the synthesis of diamond, the process of the invention is a significant improvement over known formation techniques such as high temperature/high pressure reactions, solid precipitation reactions, shock wave synthesis, CVD techniques, combustion flame techniques, etc. The present invention utilizes a novel combination of starting materials and processing conditions to result in novel materials (e.g., diamond). Specifically, with regard to diamond formation, the combination of one or more starting source(s) of carbon in a non-vapor form (e.g., certain solids liquids including, but not limited to, amorphous carbon, carbon black, carbon powder, carbon fibers, graphite, charcoal, polymer materials containing carbon, glassy carbon non-vapor carbon precursor materials, etc.) with one or more appropriate seed material(s) present in addition to the starting source of carbon or inherently present in the starting source of carbon, said seed material(s) having a diamond or diamond-like crystalline structure (e.g., diamond crystals, silicon, silicon carbide, cBN, various face-centered cubic structures which are similar to the crystal lattice of diamond, or other isostructual materials, etc.) and/or one or more seed material precursors which, under the process conditions of the invention, may form one or more seed materials in situ (e.g., Ni, Cu, Mo, Zr, Pt, Pd, etc.) may, when heated to a suitable temperature (e.g., 300xc2x0 C.-2000xc2x0 C., and more preferably 300xc2x0 C.-1600xc2x0 C. and even more preferably 700xc2x0 C.-1000xc2x0 C.) in the presence of a suitable atmosphere, either externally supplied or internally created (e.g., hydrogen and other atmospheres such as argon, nitrogen carbon, oxygen and mixtures thereof) which do not need to exceed about 1.01325xc3x97105 Pa (one (1) atmosphere) of pressure, or even pressures greater than 1.01325xc3x97105 Pa (one atmosphere), form diamond materials as coatings or as free-standing (i.e., self-supporting) bodies of various desirable sizes and shapes.
Suitable starting material mixtures for use in connection with the present invention may be formed by many conventional techniques including simply mixing solid materials together in a homogeneous or non-homogeneous manner. Such mixing may include many traditional mixing processes such as dry mixing processes (e.g., ball milling) traditional wet mixing processes, etc. A particularly preferred method for mixing solids together is known as the nanocomposite formation technique. The description of nanocomposite formation technique are well known in the literature as set forth in the following references, the subject matter of which are herein expressly incorporated by reference: Rustum Roy, Sol-Gel Processes: Origins, Problems, Products, Am. Ceram. Soc. Bull. 60:383 (1981); Rustum Roy, New Hybrid Materials made by Sol-Gel Technique, Bull. Am Ceram. Soc. 61:374 (1982); Rustum Roy, Ceramics from Solutions: Retrospect and Prospect, Mat. Res. Soc. Annual Mtg. Abstracts, p. 370 (1982); Rustum Roy, New Metal-Ceramic Hybrid Xerogels, Mat. Res. Soc. Annual Mtg. Abstracts, p 377 (1982); Rustum Roy, Ceramics by the solution-Sol-Gel Route, Science 238:1664-1669 (1987); Rustum Roy, S. Komarneni and W. Yarbrough, Some New Advances with SSG-Derived Nanocomposites, Chapter 42, Ultrastructure Processing of Advanced Ceramics, John Mackenzie and Don Ulrich (eds.), Wiley Interscience, pp. 571-588 (1988). However, in many instances, very desirable products can be formed without the need for the homogeneous mixing offered by the nanocomposite formation technique.
Many different apparatuses may be suitable for use in connection with processing the starting materials of the present invention. Some primary considerations in choosing acceptable processing apparatuses may include, for example, the ability of the apparatus to contain a controlled atmosphere and the ability to heat, at least locally, the starting materials to a sufficiently high temperature so as to permit reactions according to the present invention to occur. Accordingly, acceptable processing apparatuses include, for example, chemical vapor deposition apparatuses which are assisted by such means as, for example, microwave generator apparatuses, radio frequency generator apparatuses, filament heating apparatuses, direct heating apparatuses, etc. In addition, with regard to diamond formation, the present invention may also function acceptably in the presence of hydrogen or acetylene flames either contained within a controlled atmosphere area or not contained in a controlled atmosphere vessel.
It should be understood that this disclosure focuses primarily on the production of diamond coatings and various diamond shapes. However, despite such focus, it should be clear to an artisan of ordinary skill that the concepts of the invention translate directly in numerous parallel material systems (e.g., boron nitride), each of which material systems should be benefitted by this invention in a similar manner.
An object of the invention is to develop a new process for the manufacture of various compositions of films (e.g., diamond) using starting materials in a non-vapor form (e.g., a non-vapor source of carbon for diamond film formation).
It is a further object of the invention to develop a process for the manufacture of various self-supporting bodies (e.g., diamond) to net or near-net shape using starting materials in non-vapor form (e.g., a non-vapor source of carbon for self-supporting diamond structures).
It is also an object of the invention to develop a process for the synthesis of various materials (e.g., diamond), which process can be conducted in various reactors including CVD reactors assisted by microwave, radiowave, etc., hot-filament reactors and in the case of diamond, in the presence of a hydrogen or an acetylene flame, either contained or not contained within a closed environment.
It is also an object the invention to manufacture cubic boron nitride from an appropriate non-vapor starting material.